Chemical reactions on the Bi2Te3–Bi2Se3 section in the process of crystal growth

Abstract By methods of differential-thermal analysis and X-ray-phase analysis it is proved that the Bi 2 Te 3 –Bi 2 Se 3 section is a system with a continuous series of solid solutions, with the formation of Bi 2 Te 2 Se compound below the solidus line. The formation of this compound has been confirmed both in experiment and by thermodynamic analysis (TDA). It has been found that after zone melting the temperature values of the liquidus and solidus lines correlate with those obtained for equilibrium systems and mentioned in the literature. The boundary has been identified for the existence of Bi 2 Te 3− x Se x solid solutions, which lies at ∼14 mol% Bi 2 Se 3 (Bi 2 Te 2.58 Se 0.42 ). TDA shows chemical interactions (reactions) resulting in the formation of Bi 2 Te 2 Se. It has been found that in the two-phase zone, the Seebeck coefficient values dramatically change in a jumping manner, with the points of extremum located on the boundaries of the two-phase zone. In the zone of Bi 2 Te 2 Se compound occurrence (33.3 mol% Bi 2 Se 3 ), the values of the Seebeck coefficient and power factor are minimal.